1. Field of the Invention
The present invention relates to a sheet processing apparatus, such as a finisher or sorter, for implementing predetermined processing such as alignment and stapling on an inserted sheet material (i.e. any sheet-form recording medium such as recording paper, transfer paper, or an OHP sheet), and an image forming apparatus comprising the sheet processing apparatus.
2. Description of the Background Art
To perform a stapling operation or folding operation on a sheet member such as sheets of paper conveyed from an image forming apparatus, the sheets of paper must be aligned, and even when a user collates the sheet members, the sheet members are preferably aligned. Hence, a sheet aligning apparatus for aligning the sheet members is typically provided in a sheet processing apparatus positioned on the downstream side of the image forming apparatus. In Japanese Patent Publication No. 2,783,326 (Prior Art 1), Japanese Patent Publication No. 2,783,327 (Prior Art 2), Japanese Patent Publication No. 3,617,926 (Prior Art 3), and Japanese Patent Publication No. 3,655,407 (Prior Art 4), for example, a sheet aligning apparatus, or more particularly a rear end fence for performing an alignment operation in a sheet conveyance direction, is annexed to a staple tray for stapling the sheets, and after being aligned, the sheets are stapled and transmitted to a discharge tray. Hence, the sheet processing apparatus is provided with two trays, i.e. the staple tray and the discharge tray.
Japanese Examined Patent Application Publication H8-9451 (Prior Art 5) discloses a sheet post-processing apparatus comprising discharging means for discharging a sheet, a first tray for supporting a part of the sheet discharged by the discharging means on the upstream side of a sheet discharge direction, a second tray capable of movement in a vertical direction, for supporting a downstream side part of the sheet that is supported by the first tray at the upstream side part thereof, stapling means for stapling the sheet that is supported by the first tray at the upstream side part thereof, and moving means for moving the stapled sheet to the second tray. The first and second trays are inclined such that an upstream side part thereof is low, and thus the sheet that is discharged by the discharging means is aligned while moving along the incline in the direction of the stapling means. It is also disclosed in Prior Art 5 that the discharging means discharge the sheet such that the sheet straddles the first tray and second tray in both a stapling mode and a non-stapling mode.
Japanese Patent Publication No. 3,284,782 (Prior Art 6) discloses a paper post-processing apparatus for implementing post-processing such as stapling or hole-punching on sheets of paper discharged from an image forming unit, comprising a single compiling tray having at least a paper collecting paddle and a paper aligning plate for aligning the sheets of paper discharged from the image forming unit, a paper post-processing machine disposed at a rear end portion of the compiling tray, a loading tray on which the sheets of paper discharged from the compiling tray are loaded, and a set discharge roller for discharging the sheets of paper (a set) that have been aligned on the compiling tray to the loading tray. One end of the sheets of paper on the compiling tray contact the loading tray, and the sheets of paper discharged from the image forming unit are discharged to the loading tray as a set via the compiling tray regardless of whether or not post-processing has been performed by the paper post-processing machine.
In the background art described in Prior Art 1 to Prior Art 4, a staple tray unit is provided as a dedicated structural member for performing a stapling operation, and therefore a structure provided for the purpose of stapling must be used even when the sheets are simply to be aligned. Moreover, there is no specific description of the shape or angle of incline of the staple tray unit for aligning the sheet member, and judging by the attached drawings, the staple tray unit is constituted by a non-vertical planar member having an appropriate incline. The staple tray is not used at all in modes where sheet alignment is not performed, and at these times becomes a useless structure.
Furthermore, when the sheet member is laid substantially horizontally and an alignment operation is performed thereon, the sheet member does not move under its own weight, and therefore a sheet member moving member such as a return roller must be provided. As a result, the number of structural members for ensuring that the sheet member moves increases. In turn, this leads to increases in the number of components, the structural complexity, the weight of the machine, operating noise, and cost.
Moreover, the sheet member may be disturbed by machine vibration or the like after being aligned initially by the sheet member moving member. To prevent the aligned sheet member from being disturbed again by machine vibration or the like, a member for holding the sheet member may be added, but this also leads to corresponding increases in the number of components, the structural complexity, the weight of the machine, and the cost of the machine. In addition, since a large sheet member is laid substantially horizontally in a similar manner, the size of the machine also increases.
Further, when performing stapling processing using the stapling means, if the staple is not punched in a substantially perpendicular direction to the aligned sheet member, the staple may buckle, leading to a decrease in stapling quality or a stapling defect. When the stapling means are rotated in a substantially vertical plane for the purpose of oblique stapling, the diagonally rotated stapling means attempt, under their own weight, to return to a parallel stapling condition, making it impossible to maintain a stable attitude. Hence, during oblique stapling, the staple cannot be held at a fixed angle of incline, leading to a decrease in stapling quality.
In the background art of Prior Art 5, the sheet member straddles the first tray and second tray and is loaded at an incline such that the conveyance upstream side thereof is low. However, the sheets are discharged so as to straddle the first tray and second tray in both the stapling mode and the non-stapling mode, which is disadvantageous in terms of space conservation.
According to the background art of Prior Art 6, one end of the paper on the compiling tray contacts the loading tray. However, there is no description of the positional relationship, for example the angle and so on, between the trays, and although the machine is small in size, space must be provided for the trays on the conveyance upstream side, which is disadvantageous in terms of space conservation.
Japanese Unexamined Patent Application Publication 2004-42326 (Prior Art 7) discloses a paper processing apparatus in which a stitcher portion having a staple housing portion and an extrusion portion and a clincher portion for bending the tip ends of the staple are constituted separately, for stapling a plurality of sheets of paper existing between the two stapler members using staples. The paper processing apparatus comprises first and second moving pedestals for moving the stitcher portion and clincher portion in parallel synchronously in a direction intersecting a paper conveyance direction, first driving means for driving the first and second moving pedestals, first and second rotating pedestals supported on the same axis as, and so as to be capable of rotating relative to, the first and second moving pedestals, respectively, second driving means for rotating the first and second rotating pedestals synchronously, and control means for executing parallel stapling or oblique stapling in a desired position on the basis of a difference in the amount or speed at which the moving pedestals and rotating pedestals are moved by the first driving means and second driving means. When moving to a subsequent stapling operation after executing parallel stapling or oblique stapling, the control means execute the stapling operation by moving the stitcher portion and clincher portion to a position which is closer to a stapling position than a home position thereof, this position being preset to ensure that paper conveyance is not impeded, and by moving the stitcher portion and clincher portion from this position in a single direction relative to the stapling position at all times.
Japanese Unexamined Patent Application Publication H11-180628 (Prior Art 8) discloses a sheet post-processing apparatus in which an image-formed sheet discharged from an image forming apparatus is discharged to a discharge tray by discharging means after being stapled. In this sheet post-processing apparatus, a pair of staplers for stapling image-formed sheets of various sizes can be driven by a single drive source and thereby moved in parallel and rotated. Stapling processing is performed on sheets of various small sizes by moving the staplers in parallel in a width direction orthogonal to a sheet conveyance direction, while stapling processing is performed on sheets of various large sizes by parallel-moving and rotating the staplers.
As described above, Prior Art 7 discloses an invention in which movement and rotation in the paper width direction are performed using separate drive sources. When a sheet member stapling mode includes two stapling modes, i.e. a so-called parallel stapling mode in which the staple is punched parallel to an end portion of the sheet member and an oblique stapling mode in which the staple is punched diagonally, the stapling mode is executed by driving a driving apparatus for parallel-moving a stapler provided for parallel stapling and a driving apparatus for diagonally rotating a stapler provided for oblique stapling individually. When two dedicated driving apparatuses (drive sources) are provided in this manner, the number of components increases, leading to increases in the cost and weight of the machine.
In the invention described in Prior Art 8, a single drive source is provided, but the two staplers move along a rail and are rotated using a cam mechanism. Since only one drive source is provided, a reduction in cost can be achieved in comparison with the invention described in Prior Art 7i, but the movement range thereof is restricted, and hence the stapling position is limited. Moreover, the central portion of the paper cannot be stapled, and hence in certain cases, it may be impossible to respond to the needs of the user.
Technologies relating to the present invention are also disclosed in, e.g. Japanese Unexamined Patent Application Publication H09-136760, Japanese Unexamined Patent Application Publication H09-208116, Japanese Unexamined Patent Application Publication H10-152259, Japanese Unexamined Patent Application Publication H10-194575, Japanese Unexamined Patent Application Publication H10-120284, Japanese Unexamined Patent Application Publication H11-240665, Japanese Unexamined Patent Application Publication 2000-185868, Japanese Unexamined Patent Application Publication 2000-136067, Japanese Unexamined Patent Application Publication 2001-031323, Japanese Unexamined Patent Application Publication 2002-234665, Japanese Patent Publication No. 3,273,351, and Japanese Patent Publication No. 3,247,826.